1. Field of the Invention
This invention relates to a method of manufacturing semiconductor devices. More particularly, this invention relates to an interconnection pattern formation utilizing an aluminum film or an alloy film primarily comprising aluminum in the semiconductor device manufacture.
2. Description of the Prior Art
Conventional semiconductor devices comprising an insulating film on a semiconductor substrate, further comprising an aluminum film or an alloy film primarily comprising aluminum with a desired interconnection pattern formed thereon have been broadly used.
A conventional method of manufacturing a semiconductor device will be explained below with reference to the figures. FIGS. 3(a)-(d) illustrate a diagram of each stage of the conventional manufacturing process of a semiconductor device. In FIGS. 3(a)-(d), numeral 1 denotes a semiconductor substrate, 2 an insulating film, 3 an aluminum film or alloy film primarily comprising aluminum (hereinafter abbreviated "Al film"), 4 a mask comprising a photo resist film, 5 a deposited film.
First, an insulating film 2 is formed on a semiconductor substrate 1, and an Al film 3 is laminated thereon by a suitable method such as sputtering. Consecutively, a mask 4 comprising a photo resist film which processes the Al film 3 into a desired pattern is formed (FIG. 3(a)). Then plasma etching with a gas mixture of Cl.sub.2 and BCl.sub.3 is applied to the Al film 3. By the plasma etching, a part of the Al film not having the mask 4 formed thereon is chlorinated and removed. At that time, a deposited film of reaction product 5 primarily comprising aluminum chloride (AlCl.sub.3) is deposited on the sides of the mask 4 or the patterned Al film 3 thereunder (FIG. 3(b)). Then, plasma electric discharge is applied in the presence of CF.sub.4 gas or CHF.sub.3 gas to prevent the corrosion of the Al film 3. By the plasma electric discharge, the deposited film of reaction product 5 of chloride is substituted for fluoride (FIG. 3(c)). Then an ashing treatment is carried out by applying oxygen plasma to the mask 4 of a photo resist film to remove the mask 4, and a patterned interconnection comprising Al film 3 is formed (FIG. 3(d)).
The above-mentioned conventional technique of corrosion prevention treatment on the Al film 3 with a plasma of CF.sub.4 gas or CHF.sub.3 gas is not sufficient, and in many cases chloride tends to remain and corrodes the Al film 3. In addition, the deposited film of reaction product 5 is oxidized by the ashing treatment with oxygen plasma to become aluminum oxide and thus, becomes slightly soluble in water and difficult to remove. For such reasons, the deposited film of reaction product 5 causes defective interconnection pattern. Moreover, since it is often necessary to remove the aluminum oxide film by washing with a chemical that requires an industrial waste water treatment, such as acid, alkali, or an organic solvent, production cost tends to become higher.